This invention relates to file systems and is particularly concerned with allocation of space in a file system such as, for example, a disc file system.
In one conventional form of disc file system, the available data storage space is divided into fixed size blocks of 512 or 1024 bytes, and these blocks are allocated to files as required. A problem with this, however, is that it is unlikely that the blocks allocated to a particular file will be contiguous on the disc, and the blocks are small compared with the size of a typical large file. Thus, if a large amount of data needs to be read from the disc, there will be much disc head movement, which reduces the rate at which the data can be read.
One way of alleviating this problem would be to increase the block size, so as to increase the degree of contiguity of the files, and thereby to reduce the amount of head movement. However, increasing the block size leads to the further problem that small files (i.e. those significantly smaller than the block size) would waste an unacceptable amount of space.
Various compromise schemes have been proposed, but in general the filestore eventually becomes fragmented so that little contiguous space is available, and some tidying up process is required.
The object of the present invention is to provide an improved file system in which the above problems are overcome.